1. Field of the Invention
The present invention generally relates to detecting a fixed pattern, in particularly, relates to detecting an edge of the fixed pattern.
2. Description of Related Art
Dynamic image display indicates displaying multiple images at a desired frequency. The display content of the images changes over time to form dynamic images. Generally, the dynamic image display is for example playing back the images on a video camera or a TV set.
However, when the original dynamic image content is played back, a fixed-still pattern may be overlapped on the dynamic image content based on some requirements. The fixed-still pattern is for example a logo pattern, a channel letter or sign, or some other patterns. The fixed-still pattern usually remains in the still state for a while.
FIG. 1 is a schematic view of changing of a dynamic image content when played back. Referring to FIG. 1, an image content displayed at a time point is illustrated in the upper figure. The content of the image 100 for example includes an object 102 and a fixed-still pattern 104. The fixed-still pattern 104 is e.g. a logo that represents the image content and is located at a fixed position in the still state. In the lower figure of FIG. 1, the next display image is illustrated. Here, the object 102 moves to another position, but the fixed-still pattern 104 remains at the same position.
In one circumstance of the sudden disappearance of the fixed-still pattern 104, the fixed-still pattern 104 is set to be not displayed any more. However, in another circumstance, the fixed-still pattern 104 disappears suddenly for example due to noises or instability of the display content or the like. The sudden disappearance of the fixed-still pattern 104 may result in judder of the fixed-still pattern 104.
FIG. 2 is a schematic view of changing of a dynamic image content when played back. The upper figure of FIG. 2 is identical to that of FIG. 1. When the next image is displayed as shown in the lower figure of FIG. 2, the fixed-still pattern 104 disappears suddenly.
In another similar circumstance, the fixed-still pattern 104 may move to cause the judder surrounding the fixed-still pattern 104, which may result in the blocky of the fixed-still pattern 104.
However, it is hard to distinguish the disappearance of the fixed-still pattern 104 and at least the situation that a fixed structure moves periodically.
Therefore, it is a problem in need of a solution how to effectively detect an edge of a fixed-still pattern to detect whether the displayed fixed-still pattern is contained.